One day my husband and I were watching a TV show that was talking about ways to save energy. One of them is to unplug unused devices (any kind that use transformer) from the outlet when not in use. It turns out that these transformers consume power whenever they are plugged into the wall outlets, whether they are connected to a device or not. Since then we try to unplug them when not in use.
One day I told my husband: “there should be an easier way than always having to bend down and unplug these transformers from the outlets! Why don't they put a switch inside the connector that will shut down the transformer when we disconnect the device?”. Hence, this idea begins.
The power consumption of an idle transformer is not large—on the order of 1 to 10 watts per transformer. But it does add up. Let's say that you have 10 transformers, and they consume 5 watts each. That means that 50 watts are being wasted constantly. For a year you will have wasted 50*24 hours 365 days=438 kilowatt-hour. A kilowatt-hour cost about 15 cents in my area, that means that I am wasting 438*0.15=$65.7 every year down the drain.
Going up to the scale of the US—there are roughly 100 million households in the United States. If each household wastes 50 watts on these transformers, that's a total of 5 billion watts. As a nation, that's more than $750,000 dollars wasted every hour, or $6,570,000,000 wasted every year! More than 6 billion dollars of energy are wasted in the US alone for a year.
Right now the only way to save energy when a transformer is not used is to disconnect the voltage source applied to its primary winding. Most of the time this means unplugging the device from the power outlet and this requires an effort from the user and his desire to save energy.
The shortcomings are that you need to have a person that is concerned about wasting energy and also that person is willing to unplug idle transformer each time would be advantageous to provide a saving of energy by simply disconnecting the primary winding of a transformer of any unused device.
It would also be advantageous to provide a way for users not to change their habits but still make them save energy that would have been wasted other wise.
It would further be advantageous to provide an integrated switch directly to the power connector or within the turn-off circuit of the device.